The proposed research represents a continuation of studies designed to provide information on the biosynthesis and regulation of HA in the vitreous. The properties of the glycosyl transferase enzymes involved in HA synthesis will be determined in extracts of hyalocytes prepared from young calves (active synthesis) and adult steers (steady state synthesis). Using hyalocytes in culture, we will determine how the extracellular environment (concentration and molecular size of HA) affects the hyalocyte's production of HA. As an extension of studies on the production of glycosaminoglycans by hyalocytes, the production of other carbohydrate-containing vitreous macromolecules, the glycoproteins, will also be studied. The effect of HA on this process will be investigated. Hyalocytes have been classified as macrophages. Recent evidence indicates that the phagocytic properties of macrophages appear to depend on the presence of cell surface glycoprotein. We will study the biosynthesis of this cell coat and the role of cell surface glycosyl transferases in the biosynthetic pathway. BIBLIOGRAPHIC REFERENCES: Jacobson, B. Biosynthesis of Hyaluronic Acid in the Vitreous. Studies on a Particulate Hyalocyte Glycosyl Transferase. Abstracts Spring 1975 ARVO Meeting, p. 2. Jacobson, B., and Balazs, E. A. Effect of Hyaluronic Acid on Cell Metabolism. Abstracts Third International Symposium of Glycoconjugates: Functions in Animals, Brighton, England, 6-12 July, 1975, p. 11.